This invention relates generally to fuel pressure regulators of the type which are used in liquid fuel management systems such as fuel injection systems for internal combustion engines. More specifically the invention relates to an improvement in the valve portion of the pressure regulator.
In a typical fuel injection system, liquid fuel is pumped from the fuel tank to the injector(s) via a fuel rail that serves the injectors. It is an accepted practice to use a fuel pressure regulator in association with the fuel rail to set a pressure limit at which fuel is delivered to the injector(s). The pressure regulator also serves to dampen pressure surges and to keep the rail pressurized when the system is shut off.
While various embodiments of fuel pressure regulators are disclosed in prior patents, they generally share a number of similarities. A liquid fuel chamber portion of the pressure regulator is in communication with the fuel rail to pressure-regulate the fuel pumped into the rail from the tank. The liquid fuel chamber is separated from a control chamber portion by a movable wall that carries a valve disposed within the chamber. The control chamber comprises a control means for controlling response of the movable wall to pressure conditions in the liquid fuel chamber. The valve controls an orifice through which excess fuel is returned to tank. The movable wall is positioned in accordance with the forces acting on its opposite sides, thereby setting the effective size of the orifice. In this way, excess pressure is relieved, resulting in fairly well regulated pressure being established for the liquid fuel in the rail.
In most pressure regulators the orifice comprises a seat for the valve, and the valve closes and opens the orifice by seating on and unseating from the orifice seat. The control means typically comprises a helical coil spring disposed within the control chamber and acting on the movable wall to urge the valve toward closure of the orifice. The control means can also comprise a port for communication of the control chamber to a fluid pressure reference such as manifold, vacuum for example. The movable wall which carries the valve is typically an annular diaphragm whose outer periphery is held between mating edges of the two halves of the pressure regulator housing. The inner periphery of the diaphragm is held between a member which is toward the control chamber side to form a seat for the control spring and a mounting which is toward the liquid fuel chamber side for mounting of the valve on the movable wall.
Various types of valves are illustrated in prior fuel pressure regulator patents. The importance of securing proper alignment between the valve and the seat is evident, and these patents suggest various means for obtaining this result. The use of spheres is shown in U.S. Pat. Nos. 3,106,219; 3,511,270; and 4,627,463. The use of circular discs is also shown in a number of patents. In many of these disc designs, the disc is physically attached to a sphere which can swivel in its mounting on the diaphragm. For examples of such disc-sphere combinations, attention is directed to U.S. Pat. Nos. 4,327,767; 4,431,026; 4,505,296; and 4,653,528. One U.S. Pat. No. 4,559,968, even shows a sphere attached to a sphere. The use of a truncated sphere is also known, as evidenced by U.S. Pat. No. 4,237,924.
On the basis of the extensive use of spheres in prior patents on this subject, it should be apparent that the swivelling capability which is obtained through the use of a sphere is very advantageous in taking out misalignment which otherwise may exist in a liquid fuel pressure regulator between the valve and seat. Likewise the use of flat discs suggests their importance in securing full closure of a valve with a flat seat.
Despite the existence of these attributes in various prior fuel pressure regulators, the processes by which their valves are manufactured tend to complicate the fabrication process. A sphere per se is not difficult to manufacture; however, when a circular disc must be attached to it, the prior processes have resorted to the use of welding, soldering or the like to join the two parts together. Since the parts are physically small, such joining procedures are rather intricate. Furthermore, they add to the production cost because they require suitable equipment to perform the joining, and this joining constitutes an additional operation in the overall fabrication process. While the truncated sphere embodiment of U.S. Pat. No. 4,237,924 would appear to combine the benefits of the sphere-disc combinations without the necessity of the joining operation, the step of taking a hardened sphere and truncating it is not a simple task either. It may still be necessary to conduct further processing of both disc-sphere combinations and truncated spheres in order to render them suitable for use as fuel pressure regulator valves.
The nature of the particular material used in such valves is also an important consideration for several reasons. Liquid fuels, such as gasoline, are highly corrosive, and the materials employed must withstand this severe environment. In the disc-sphere combination, the material of the disc and that of the sphere must be compatible with the particular joining medium which is employed. In the case of the truncated sphere, the truncation may require treatment of its surface and finish.
The present invention relates to improvements in fuel pressure regulator valves which embody the attributes of swivelling and a flat surface for coaction with a seat, but free of certain of the constraints of the prior designs described above. One important advantage of the invention is that the portion of the valve which seats on the seat can be of a material diverse from that of the portion of the valve which provides the swivelling capability. The invention discloses the valve construction as two separate parts assembled together without the use of joining procedures such as welding or soldering. Elimination of joining procedures is another advantage.
One part of the valve is spherically contoured and captured in a mounting on the movable wall (diaphragm) for swivelling. This one part contains a hole which lies on a radial and which in general is toward the seat over the part's swivel mounting on the movable wall. This swivel mounting results in the axis of the hole being positionable within a conical zone of swivelling conspherical with the spherical contour of the part.
The second part of the valve is a stem which comprises a circular head and a shank which extends from the head. The stem is operatively related to the spherically contoured part by fitting the stem's shank into the hole in the spherically contoured part. Preferably the shank is press-fitted to the hole until the head abuts the spherically contoured part around the hole's opening. The head is preferably in the shape of a flat circular disc.
Consequently, the resultant two-part valve is endowed both with swivelling capability within its mounting on the diaphragm by virtue of the spherically contoured part, and with a flat closure surface for seating against the seat by virtue of the shape of the stem's head.
The preferred mounting comprises a receptacle space within which the spherically contoured part is captured. While the receptacle space is designed to preclude appreciable bodily displacement of the spherically contoured part within the receptacle space, limited bodily displacement along the line of action toward and away from the seat. combined with swivelling, is present in the mounting. A small compression spring within the mounting exerts a force on the valve in a direction toward the seat. When the valve is seated, it is slightly retracted into the receptacle space. When the valve is unseated, the small spring urges the spherically contoured part against an annular bearing surface of the mounting which captures the spherically contoured part in the receptacle space. The force exerted by the small spring, as reacted against this annular surface, serves to hold the unseated valve in the particular swivel orientation which it assumed when last seated. The unseating of the valve is very uniform around the circumference of the orifice, a distinct advantage. The orientation is maintained for subsequent uniform closing, but in any event, the valve is self-aligning with the orifice upon closing, thereby essentially eliminating the movable wall (diaphragm) as a source of imperfection in securing full closing. In other words, whenever the valve closes, it always finally attains the same full closure, despite diaphragm tipping or distortion.
Two particular embodiments of the invention are disclosed herein. In one embodiment the spherically contoured part is a sphere, and the hole is a blind one which is drilled partially into the sphere. The small spring engages the spherical surface of the sphere in the hemisphere opposite the hemisphere where the head of the stem is disposed.
In the second embodiment, the spherically contoured part is a truncated sphere having parallel truncations in opposite hemispheres. The hole is a through-hole extending from the center of one truncation, through the center of the sphere, and to the center of the opposite truncation. The shank of the stem extends completely through and beyond the through-hole. The distal end surface of the shank is spherically contoured to the same spherical contour as that of the truncated sphere, and it is disposed at the same radius from the center of the truncated sphere as is the truncated sphere's own spherical surface. The small spring within the mounting bears against the distal end of the shank. The zone of swivelling is limited by abutment of the head of the stem with an annular lip of the mounting which contains the annular bearing surface which captures the truncated sphere within the mounting. The parts are proportioned such that the small spring is precluded from riding off the distal end of the shank within the defined conical zone of swivelling. The truncated sphere is advantageously fabricated by powdered metal fabrication techniques while the stem is a machined metal part.